U.S. patent application number 14/372552 was filed with the patent office on 2015-07-02 for multi-pass hyperfiltration system.
This patent application is currently assigned to DOW GLOBAL TECHNOLOGIES LLC. The applicant listed for this patent is Dow Global Technologies LLC. Invention is credited to Markus Busch, Jon E. Johnson, Steven D. Jons, Katariina Majamaa, Steven Rosenberg.
Application Number | 20150182918 14/372552 |
Document ID | / |
Family ID | 47755074 |
Filed Date | 2015-07-02 |
United States Patent
Application |
20150182918 |
Kind Code |
A1 |
Johnson; Jon E. ; et
al. |
July 2, 2015 |
MULTI-PASS HYPERFILTRATION SYSTEM
Abstract
The present invention is directed toward a multi-pass
hyperfiltration system (38) including at least two passes (42,44)
of spiral wound modules positioned in series along a fluid pathway;
including: a first pass is located upstream along the fluid pathway
with respect to a second pass such that permeate from the first
pass is directed along the fluid pathway (40) to the second pass,
and each pass comprises a pressure vessel enclosing at least one
spiral wound module, each module including at least one
hyper-filtration membrane envelop and feed spacer sheet wound about
a permeate collection tube, wherein the system is characterized by
the first pass comprising a spiral wound module including a feed
spacer sheet having a thickness greater 0.65 mm and the second pass
comprising a spiral wound module including a feed spacer sheet
having a thickness less than 0.65 mm.
Inventors: |
Johnson; Jon E.; (Plymouth,
MN) ; Busch; Markus; (Tarragona, ES) ;
Majamaa; Katariina; (Tarragona, ES) ; Rosenberg;
Steven; (Shorewood, MN) ; Jons; Steven D.;
(Eden Prairie, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Global Technologies LLC |
Midland |
MI |
US |
|
|
Assignee: |
DOW GLOBAL TECHNOLOGIES LLC
Midland
MI
|
Family ID: |
47755074 |
Appl. No.: |
14/372552 |
Filed: |
February 20, 2013 |
PCT Filed: |
February 20, 2013 |
PCT NO: |
PCT/US2013/026788 |
371 Date: |
July 16, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61605993 |
Mar 2, 2012 |
|
|
|
Current U.S.
Class: |
210/652 ;
210/437 |
Current CPC
Class: |
B01D 2313/14 20130101;
B01D 2317/025 20130101; B01D 2313/143 20130101; B01D 2317/02
20130101; B01D 61/025 20130101; B01D 63/12 20130101 |
International
Class: |
B01D 63/12 20060101
B01D063/12; B01D 61/02 20060101 B01D061/02 |
Claims
1. A multi-pass hyperfiltration system comprising at least two
passes of spiral wound modules positioned in series along a fluid
pathway, wherein; a first pass is located upstream along the fluid
pathway with respect to a second pass such that permeate from the
first pass is directed along the fluid pathway to the second pass,
and wherein each pass comprises a pressure vessel enclosing at
least one spiral wound module, the module comprising at least one
hyperfiltration (RO or NF) membrane envelop and feed spacer sheet
wound about a permeate collection tube; the system being
characterized by the first pass comprising a spiral wound module
including a feed spacer sheet having a thickness of 0.7 to 1.2-mm
and the second train comprising a spiral wound module including a
feed spacer sheet having thicknesses of 0.3 to 0.6 mm.
2. The system of claim 1 wherein the second train comprises a
spiral wound module including feed spacer sheet having a thickness
less than or equal to 0.56 mm (2 mil).
3. (canceled)
4. The system of claim 1 wherein each pass comprises a pressure
vessel enclosing at least two spiral wound modules connected in
series, wherein all the spiral wound modules of a given pass are of
the same type.
5. A method for filtering a liquid having a TOC value of at least 1
ppm, comprising pressurizing a feed liquid and directing the feed
liquid through a first pass of hyperfiltration to produce a first
permeate liquid, directing the first permeate liquid through a
second pass of hyperfiltration to produce a second permeate liquid,
wherein: both passes comprises a pressure vessel enclosing at least
one spiral wound module, the module comprising at least one
hyperfiltration (RO or NF) membrane envelop and feed spacer sheet
wound about a permeate collection tube and the first pass
comprising a spiral wound module including a feed spacer sheet
having a thickness pf 0.7 tp 1.2 mm and the second train comprising
a spiral wound module including a feed spacer sheet having
thicknessess of 0.3 to 0.6 mm.
6. The method of claim 5 wherein the second train comproses a
spiral wound module including feed spacer sheet having a thickness
less than or equal to 0.56 mm (22 mil).
7. (canceled)
8. The method of claim 5 wherein each pass comprises a pressure
vessel enclosing at least two spiral wound modules connected in
series wherein all the spiral wound modules on a given pass are of
the same type.
9. (canceled)
Description
FIELD
[0001] The invention generally relates to multi-pass
hyperfiltration systems including multiple operating units (trains)
interconnected such that permeate from an upstream unit is utilized
as feed in a downstream unit.
INTRODUCTION
[0002] Spiral wound modules used in hyperfiltration include at
least one membrane envelop and feed spacer sheet wound about a
permeate collection tube. The use of a thinner feed spacer sheet
allows more active membrane area to be packed within a spiral wound
module while maintaining a given diameter. While the incorporation
of additional active membrane within the module generally improves
separation efficiency, the use of thinner feed spacers can lead to
increased fouling particularly with feed liquids having total
organic content (TOC) values greater than 1 ppm, (as measured by
ASTM D 4839-03). Fouling in turn leads to reduced flux and
increased pressure loss.
SUMMARY
[0003] A multi-pass hyperfiltration system including at least two
passes of spiral wound modules positioned in series along a fluid
pathway. The system includes a first pass located upstream along
the fluid pathway with respect to a second pass such that permeate
from the first pass is directed along the fluid pathway to the
second pass. Each pass includes a pressure vessel enclosing at
least one spiral wound module, with each module comprising at least
one hyperfiltration membrane envelop and feed spacer sheet wound
about a permeate collection tube. The system is characterized by
the first pass comprising a spiral wound module including a feed
spacer sheet having a thickness greater than 0.65 mm and the second
pass comprising a spiral wound module including a feed spacer sheet
having a thickness less than 0.65 mm. Systems including this
combination of features can achieve the benefits associated with
thinner feed spacer sheets while reducing much of the fouling
typically associated therewith.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a perspective, partially cut-away view of a spiral
wound filtration module.
[0005] FIG. 2 is a schematic view of a multi-pass filtration
system.
DETAILED DESCRIPTION
[0006] The present invention includes spiral wound elements
("modules") suitable for use in reverse osmosis (RO) and
nanofiltration (NF). Such modules include one or more RO or NF
membrane envelops and feed spacer sheets wound about a permeate
collection tube. RO membranes used to form envelops are relatively
impermeable to virtually all dissolved salts and typically reject
more than about 95% of salts having monovalent ions such as sodium
chloride. RO membranes also typically reject more than about 95% of
inorganic molecules as well as organic molecules with molecular
weights greater than approximately 100 Daltons. NF membranes are
more permeable than RO membranes and typically reject less than
about 95% of salts having monovalent ions while rejecting more than
about 50% (and often more than 90%) of salts having divalent
ions--depending upon the species of divalent ion. NF membranes also
typically reject particles in the nanometer range as well as
organic molecules having molecular weights greater than
approximately 200 to 500 Daltons. For purposes of the present
description, the term "hyperfiltration" collectively describes RO
and NF.
[0007] A representative spiral wound filtration module is generally
shown at 2 in FIG. 1. The module (2) is formed by concentrically
winding one or more membrane envelopes (4) and feed spacer sheet(s)
("feed spacers") (6) about a permeate collection tube (8). Each
membrane envelope (4) preferably comprises two substantially
rectangular sections of membrane sheet (10, 10'). Each section of
membrane sheet (10, 10') has a membrane or front side (34) and
support or back side (36). The membrane envelope (4) is formed by
overlaying membrane sheets (10, 10') and aligning their edges. In a
preferred embodiment, the sections (10, 10') of membrane sheet
surround a permeate channel spacer sheet ("permeate spacer") (12).
This sandwich-type structure is secured together, e.g. by sealant
(14), along three edges (16, 18, 20) to form an envelope (4) while
a fourth edge, i.e. "proximal edge" (22) abuts the permeate
collection tube (8) so that the inside portion of the envelope (4)
(and optional permeate spacer (12)) is in fluid communication with
a plurality of openings (24) extending along the length of the
permeate collection tube (8). The module (2) preferably comprises a
plurality of membrane envelopes (4) separated by a plurality of
feed spacers sheets (6). In the illustrated embodiment, membrane
envelopes (4) are formed by joining the back side (36) surfaces of
adjacently positioned membrane leaf packets. A membrane leaf packet
comprises a substantially rectangular membrane sheet (10) folded
upon itself to define two membrane "leaves" wherein the front sides
(34) of each leaf are facing each other and the fold is axially
aligned with the proximal edge (22) of the membrane envelope (4),
i.e. parallel with the permeate collection tube (8). A feed spacer
sheet (6) is shown located between facing front sides (34) of the
folded membrane sheet (10). The feed spacer sheet (6) facilitates
flow of feed fluid in an axial direction (i.e. parallel with the
permeate collection tube (8)) through the module (2). While not
shown, additional intermediate layers may also be included in the
assembly. Representative examples of membrane leaf packets and
their fabrication are further described in U.S. Pat. No. 7,875,177
to Haynes et al.
[0008] During module fabrication, permeate spacer sheets (12) may
be attached about the circumference of the permeate collection tube
(8) with membrane leaf packets interleaved therebetween. The back
sides (36) of adjacently positioned membrane leaves (10, 10') are
sealed about portions of their periphery (16, 18, 20) to enclose
the permeate spacer sheet (12) to form a membrane envelope (4).
Suitable techniques for attaching the permeate spacer sheet to the
permeate collection tube are described in U.S. Pat. No. 5,538,642
to Solie. The membrane envelope(s) (4) and feed spacer(s) (6) are
wound or "rolled" concentrically about the permeate collection tube
(8) to form two opposing scroll faces (30, 32) at opposing ends and
the resulting spiral bundle is held in place, such as by tape or
other means. The scroll faces of the (30, 32) may then be trimmed
and a sealant may optionally be applied at the junction between the
scroll face (30, 32) and permeate collection tube (8), as described
in U.S. Pat. No. 7,951,295 to Larson et al. Long glass fibers may
be wound about the partially constructed module and resin (e.g.
liquid epoxy) applied and hardened. In an alternative embodiment,
tape may be applied upon the circumference of the wound module as
described in US U.S. 2011/0094660 to McCollam. The ends of modules
may be fitted with an anti-telescoping device or end cap (not
shown) designed to prevent membrane envelopes from shifting under
the pressure differential between the inlet and outlet scroll ends
of the module. The end cap is commonly fitted with an elastomeric
seal (not shown) to form a tight fluid connection between the
module and a pressure vessel (not shown). Examples of end cap
designs include those described in U.S. Pat. No. 6,632,356 to
Hallan, et al. and U.S. 2011/0042294 to Bonta et al along with
FilmTec Corporation's iLECFM interlocking end caps. The outer
housing of a module may include fluid seals to provide a seal
within the pressure vessel as described in U.S. Pat. Nos. 6,299,772
and 6,066,254 to Huschke et al. and U.S. Pat. No. 8,110,016 to
McCollam.
[0009] Materials for constructing various components of spiral
wound modules are well known in the art. Suitable sealants for
sealing membrane envelopes include urethanes, epoxies, silicones,
acrylates, hot melt adhesives and UV curable adhesives. While less
common, other sealing means may also be used such as application of
heat, pressure, ultrasonic welding and tape. Permeate collection
tubes are typically made from plastic materials such as
acrylonitrile-butadiene-styrene, polyvinyl chloride, polysulfone,
poly (phenylene oxide), polystyrene, polypropylene, polyethylene or
the like. Tricot polyester materials are commonly used as permeate
spacers. Additional permeate spacers are described in U.S.
2010/0006504. Representative feed spacers include polyethylene,
polyester, and polypropylene mesh materials such as those
commercially available under the trade name VEXAR.TM. from Conwed
Plastics. Preferred feed spacers are described in U.S. Pat. No.
6,881,336 to Johnson.
[0010] The membrane sheet is not particularly limited and a wide
variety of materials may be used, e.g. cellulose acetate materials,
polysulfone, polyether sulfone, polyamides, polyvinylidene
fluoride, etc. A preferred membrane sheet includes FilmTec
Corporation's FT-30.TM. type membranes, i.e. a flat sheet composite
membrane comprising a backing layer (back side) of a nonwoven
backing web (e.g. a non-woven fabric such as polyester fiber fabric
available from Awa Paper Company), a middle layer comprising a
porous support having a typical thickness of about 25-125 .mu.m and
top discriminating layer (front side) comprising a thin film
polyamide layer having a thickness typically less than about 1
micron, e.g. from 0.01 micron to 1 micron but more commonly from
about 0.01 to 0.1 .mu.m. The backing layer is not particularly
limited but preferably comprises a non-woven fabric or fibrous web
mat including fibers which may be orientated. Alternatively, a
woven fabric such as sail cloth may be used. Representative
examples are described in U.S. Pat. No. 4,214,994; U.S. Pat. No.
4,795,559; US 5,435,957; U.S. Pat. No. 5,919,026; U.S. Pat. No.
6,156,680; U.S. Pat. No. 2008/0295951 and U.S. Pat. No. 7,048,855.
The porous support is typically a polymeric material having pore
sizes which are of sufficient size to permit essentially
unrestricted passage of permeate but not large enough so as to
interfere with the bridging over of a thin film polyamide layer
formed thereon. For example, the pore size of the support
preferably ranges from about 0.001 to 0.5 .mu.m. Non-limiting
examples of porous supports include those made of: polysulfone,
polyether sulfone, polyimide, polyamide, polyetherimide,
polyacrylonitrile, poly(methyl methacrylate), polyethylene,
polypropylene, and various halogenated polymers such as
polyvinylidene fluoride. The discriminating layer is preferably
formed by an interfacial polycondensation reaction between a
polyfunctional amine monomer and a polyfunctional acyl halide
monomer upon the surface of the microporous polymer layer. Due to
its relative thinness, the polyamide layer is often described in
terms of its coating coverage or loading upon the porous support,
e.g. from about 2 to 5000 mg of polyamide per square meter surface
area of porous support and more preferably from about 50 to 500
mg/m.sup.2. The polyamide layer is preferably prepared by an
interfacial polycondensation reaction between a polyfunctional
amine monomer and a polyfunctional acyl halide monomer upon the
surface of the porous support as described in U.S. Pat. No.
4,277,344 and U.S. Pat. No. 6,878,278. More specifically, the
polyamide membrane layer may be prepared by interfacially
polymerizing a polyfunctional amine monomer with a polyfunctional
acyl halide monomer, (wherein each term is intended to refer both
to the use of a single species or multiple species), on at least
one surface of a porous support. As used herein, the term
"polyamide" refers to a polymer in which amide linkages
(--C(O)NH--) occur along the molecular chain. The polyfunctional
amine and polyfunctional acyl halide monomers are most commonly
applied to the porous support by way of a coating step from
solution, wherein the polyfunctional amine monomer is typically
coated from an aqueous-based or polar solution and the
polyfunctional acyl halide from an organic-based or non-polar
solution.
[0011] Arrows shown in FIG. 1 represent the approximate flow
directions (26, 28) of feed and permeate fluid (also referred to as
"product" or "filtrate") during operation. Feed fluid enters the
module (2) from an inlet scroll face (30) and flows across the
front side(s) (34) of the membrane sheet(s) and exits the module
(2) at the opposing outlet scroll face (32). Permeate fluid flows
along the permeate spacer sheet (12) in a direction approximately
perpendicular to the feed flow as indicated by arrow (28). Actual
fluid flow paths vary with details of construction and operating
conditions.
[0012] While modules are available in a variety of sizes, one
common industrial RO module is available with a standard 8 inch
(20.3 cm) diameter and 40 inch (101.6 cm) length. For a typical 8
inch diameter module, 26 to 30 individual membrane envelopes are
wound around the permeate collection tube (i.e. for permeate
collection tubes having an outer diameter of from about 1.5 to 1.9
inches (3.8 cm 4.8)).
[0013] The pressure vessels used in the present invention are not
particularly limited but preferably include a solid structure
capable of withstanding pressures associated with operating
conditions. The vessel structure preferably includes a chamber
having an inner periphery corresponding to that of the outer
periphery of the spiral wound modules to be housed therein. The
length of the chamber preferably corresponds to the combined length
of the elements to be sequentially (axially) loaded, e.g. 1 to 8
elements, see U.S. 2007/0272628 to Mickols. The pressure vessel may
also include one or more end plates that seal the chamber once
loaded with modules. The vessel further includes at least one fluid
inlet and outlet preferably located at opposite ends of the
chamber. The orientation of the pressure vessel is not particularly
limited, e.g. both horizontal and vertical orientations may be
used. Examples of applicable pressure vessels, module arrangements
and loading are described in: U.S. Pat. No. 6,074,595, U.S. Pat.
No. 6,165,303, U.S. Pat. No. 6,299,772 and U.S. 2008/0308504.
Manufacturers of pressure vessels include Pentair of Minneapolis
Minn., Bekaert of Vista Calif. and Bel Composite of Beer Sheva,
Israel. An individual pressure vessel or a group of vessels working
together, each equipped with one or more modules, are commonly
referred to as a "train" or "pass." The vessel(s) within the pass
may be arranged in one or more stages, wherein each stage contains
one or more vessels operating in parallel with respect to a feed
fluid. Multiple stages are arranged in series, whereby the
concentrate fluid from an upstream stage is used as feed fluid for
the downstream stage, while the permeate from each stage is
collected without further reprocessing within the pass. Multi-pass
hyperfiltration systems are constructed by interconnecting
individual passes along a fluid path way as described in: U.S. Pat.
No. 4,156,645, U.S. Pat. No. 6,187,200 and U.S. Pat. No.
7,144,511.
[0014] FIG. 2 illustrates a multi-pass filtration system (38)
including two passes of spiral wound modules positioned in series
along a fluid pathway (40) with a first pass (42) located upstream
along the fluid pathway (40) with respect to a second pass (44).
Each pass (42, 44) includes a pressure vessel enclosing at least
one and preferably at least three spiral wound modules connected in
series with each module comprising at least one hyperfiltration
membrane envelop and feed spacer sheet wound about a permeate
collection tube as previously described with reference to FIG. 1.
In operation, pressurized feed liquid enters the first pass (42)
via feed inlet (46). A first permeate liquid (filtrate) exits via
outlet (48) and enters the second pass (44) via inlet (50). A
second permeate liquid exits the second pass (44) via permeate
outlet (52). Concentrate liquid exits both passes (42, 44) by way
of concentrate outlets (56, 56'). Concentrate fluid may be
discarded, recycled, used in a separate stage, or otherwise
disposed of. While shown as including two passes, the system may
include additional passes including optionally passes in parallel
along the fluid pathway. In the embodiment illustrated in FIG. 2,
the fluid pathway (40) comprises the inlets (46, 50), outlets (48,
52) first and second passes (42, 44) and piping therebetween. The
system may further include pumps (58), valves and related equipment
as is convention in the art.
[0015] The first pass (42) includes at least one spiral wound
module including a feed spacer sheet having a thickness greater
than 0.65 mm whereas the second pass (44) includes at least one
spiral wound module including a feed spacer sheet having a
thickness less than 0.65 mm. In one embodiment, the thickness of
the feed spacer sheet of the first pass is from 0.7 mm to 1.2 mm
and more preferably from 0.7 to 1 mm. In another embodiment, the
thickness of the feed spacer sheet of the second pass is from 0.3
to 0.6 mm, and more preferably 0.4 to 0.56 mm. While the individual
modules of a given pass need not be the same nor have identical
feed spacer sheets, (e.g. see U.S. 2007/0272628 to Mickols), the
feed spacer sheets of a given pass preferably meet the preceding
criteria. For purposes of the present description, the thickness of
the feed spacer sheet is determined by first measuring the combined
thickness of the feed spacer and membrane envelope. This is
preferably done using a fully assembled, non-pressurized module
provided in a dry state. The combined thickness is the quotient of
the scroll end-area and the length of the membrane envelope,
measured perpendicular to the permeate collection tube. From the
combined thickness, the thickness attributed by the membrane
envelope (e.g. membrane sheets and permeate spacer sheet if
present) is subtracted and the remaining thickness is that of the
feed spacer sheet.
EXAMPLES
[0016] Several two pass hyperfiltration system were tested. The
general layout of the systems is illustrated in FIG. 2. The first
pass consisted of a spiral wound module incorporating a standard
(90.degree. hydrodynamic angle) feed spacer sheet having a
thickness of 0.71 mm (28 mil). The second pass consisted of a
spiral wound module incorporating a standard feed spacer sheet
having a thickness of 0.56 mm (22 mil). The systems were tested
using pressurized pre-treated municipal waste water having a TOC of
approximately 7-8 ppm as measured by ASTM D 4839-03 (persulfate
oxidation). After over 60 days of continuous operation (at approx.
533 l/h), the spiral wound module of the second pass experience no
measurable pressure loss.
[0017] By way of comparison, two additional systems were tested
under the same operating conditions and liquid feed. Both
comparison systems included a first pass of ultrafiltration
(SPF-2880 pressurized ultrafiltration modules commercially
available from The Dow Chemical Company) followed by a second pass
of hyperfiltration. In comparative system A, the second pass of
hyperfiltration was identical to the first pass described in the
preceding paragraph and in comparison system B, the second pass was
identical to the second pass described in the preceding paragraph,
i.e. using a feed spacer sheet having a thickness of 0.71 mm (28
mil) and 0.56 mm (22 mil), respectively. After approximately 60
days of continuous operation (approx 537 l/h for UF, 533 l/h for
hyperfiltration), comparison system A experienced a change in
pressure loss of 58% whereas comparison system B experienced a
change in pressure loss of 161%. As indicated by this result, the
use of ultrafiltration was insufficient to prevent significant
pressure loss in downstream hyperfiltration systems when utilizing
feed liquids having TOC values above 1 ppm.
[0018] In preferred embodiments of the invention, the feed liquid
has a TOC value of at least 1 ppm but more pronounced benefits are
achieved using feed waters having TOC values of at least 3 ppm, 6
ppm or 7 ppm.
[0019] Many embodiments of the invention have been described and in
some instances certain embodiments, selections, ranges,
constituents, or other features have been characterized as being
"preferred". Such designations of "preferred" features should in no
way be interpreted as an essential or critical aspect of the
invention. Expressed ranges specifically include end points.
[0020] The entire content of each of the aforementioned patents and
patent applications are incorporated herein by reference.
* * * * *